He insisted he had often seen "very inaccurate exit polls" during his career.

"You expect me to speculate on what I regard to be a certain error, I'm not going to do it," he said.

Questioned about whether the Lib Dems would form another coalition with the Tories, he said: "I am clear that the Liberal Democrats have an appetite for doing what they've done before, which is putting national interests first."

SNP leader Nicola Sturgeon, who is forecast to be about to see her party take all but one of Scotland's seats, tweeted: "I'd treat the exit poll with HUGE caution. I'm hoping for a good night but I think 58 seats is unlikely!"

Michael Gove immediately moved to claim victory, should the exit poll prove correct.

"If the exit poll is right, it means the Conservatives have clearly won this election and Labour have clearly lost it," he told the BBC.